Friction bodies



Patented May 2, 1939 PATENT OFFICE FRICTION BODIES Karl Wolf, Ludwigshafen-on-the-Rhine, and

Hans Scheuermann, Oggersheim, signers to I. G. Farbenindustrie Germany, as- Aktiengesellschaft, Frankfort-on-the-Main, Germany,

No Drawing. Application rial No. 186,812. 1937 January 25, 1938, See- In Germany February 3,

7 Claims. (Cl. 100-v.5)

The present invention relates to friction bodies. In the preparation of friction bodies, as for example brake linings and clutch bodies, it is known to use as binding agents condensation products of polyhydric alcohols and polybasic acids, if desired with the addition of monobasic acids, monohydric alcohols and/or drying oils. Such friction bodies have a number of drawbacks, however. For example brake linings prepared from asbestos and a condensation product of polybasic aliphatic or aromatic saturated or un-' saturated acids, such as adipic acid, maleic acid or phthalic acid, and polyhydric alcohols; such as glycerine, with or without the addition of drying oils, have friction values which are very greatly dependent on temperature and in some cases, even when the initial value is high, fall after long use to values at which no suflicient braking action is obtained.

A further drawback in some cases lies in the very long hardening periods, i. e. the time necessary to convert the still soluble condensation products which fuse at elevated temperature into the insoluble and infusible state. These hardening periods are especially long when the condensation products contain drying oils and require a certain amount of oxygen for thorough hardening.

We have now found that friction bodies, 1. e. brake and clutch bodies, which are free from the said drawbacks and have especially good properties are obtained by using as the binding agent condensation products capable of being hardened which have been derived from polyhydric alcohols, such as glycols, glycerine, trimethylol propane, pentaerythritol, polyglycols, polyglycerlne or other polymerized alcohols and polybasic acids, such as phthalic acid, succinic acid, adipic acid, maleic acid and the like, as well as natural resin acids, in particular colophony or the abietic acids contained therein, or their derivatives, as for example esters.

When alpha-beta-unsaturated acids, such as maleic acid, are used as polybasic acids, these may also be caused to react with the natural resin acids or their esters before the condensation with the polyhydric alcohols.

As polyhydric alcohols, the condensation products may also contain highly polymerized alco- Brake linings prepared from the said conden may be ground with each other and pressed while hot when the condensation products are available in a solid form capable of being ground. It is more advantageous, the asbestos with a solution of the condensation product and then to dry preliminarily at from 140 to 150 C. for some hours. The dried material, which is usually somewhat agglomerated, is then ragged out again in the cold in a tearing or crushing apparatus, whereby in the following pressing process a good felting of the fibres is obtained and weak places in the pressed article are avoided. The loose fibres are preferably pressed by first laying a thin strip of paper or metal in the mould which isat a temperature of from 120 to 175 a uniform layer and covering them with a similar strip. The pressing is then effected advanhowever, to impregnate C., then laying the fibres in in if tageously at pressures of from 50 to 250 kilograms per square centimeter. After opening the mould, the pressed article may readily be removedfrom the mould because the strips prevent sticking. The hardening is effected in a chamber at from 150 to 250 c.

When preparing brake or clutch bodies from plaited or woven material, as for example woven asbestos, with or without wire insertions, the woven material is preferably impregnated with a solution of the condensation product, dried while heating and pressed.

The following examples will further illustrate how this invention may be carried out in practice, but the invention is not restricted to these examples. The parts are by weight.

Example 1 A mixture of 296 parts of a condensation product (acid value from 15 to 20) obtained by heating 1 molecular proportion of phthalic anhydride with 2 molecular proportions of glycerine at from 200 to 250 0., 100 parts of colophony and 97.3 parts of adipic acid is heated at from 180 to 220 C. for 2 hours. After cooling to 100' C., suflicient ethyl alcohol is added to form an about 60 per cent solution.

180 parts this solution are mixed with 200 parts of short-flbred asbestos in a kneading machine. The whole is then dried for about hours atirom 140 to 150 C. The dried, somewhat agglomerated material is loosened again between crushing and tearing rollers.

A thin strip of paper, of a thickness depending on the finished lining, is laid in a brake lining mould which is at a temperature of from 185 to 170 C. The loose, impregnated asbestos is then laid uniformly in the mould, a second strip of paper laid on and the mould closed. Alter pressing for 5 minutes at a pressure of 150 kilograms per square centimeter, a pressed article is obtained which may be removed from the mould readily. After hardening for 12 hours at from 150 to 200 C., it yields a brake lining having excellent properties. The wear during braking is only about half of that of a brake lining prepared with a phenol resin.

Example 2 296 parts of a condensation product prepared from glycerine and phthalic anhydride accordins to Example 1 and 286 parts oi a condensation product of 1 molecular proportion of maleic acid and 1 molecular proportion of abietic acid are heated for 2% hours at from 200 to 230 C. The product is poured into dishes while stillhot and ground after solidification. 6'7 parts of the product are ground for half an hour in a ball mill with 200 parts of short-flbred asbestos and the ground material is pressed and hardened in the manner described in Example 1.

Example 3 A solution of 128 parts or polymerized vinyl acetate in 200 parts of alcohol is allowed to flow at 140 C. while stirring well. and continuously distilling oi! the alcohol into a condensation product obtained by condensing 116 parts of maleic acid and 330 parts oi abietic acid with 69 parts of glycerine in the presence of 200 parts 01' xylene while continuously distilling oil xylene and water formed until the temperature in the reaction ves- 'sel has risen to about 200 0., which is the case 2,1se,sas

Bands oi woven asbestos material are laid in a 40 per cent solution oi the said condensation product for 24 hours, then driedi'or 4 hours at 140 0., brought while still hot into a mould which is either cold or at a temperature of from about 40 to 50 C. and pressed for one minute at a pressure of 200 kilograms per square centimeter. Aiter cooling, the pressed article may be removed from the mould and is entirely stable as regards shape.

By hardening for 12 hours at from 125 to 200 C., brake linings of excellent braking action are obtained.

What we claim is:

1. Friction bodies, the binding agent of which comprises hardened resinous condensation products oi polyhydric alcohols, polybasic acids and natural resin acids. V

2. Friction bodies, the binding agent of which comprises hardened resinous condensation products oi polyhydric alcohols, polybasic acids and a member of the group consisting oi colophony and the resin acids contained therein.

3. Friction bodies, the binding agent of which comprises hardened resinous condensation products oi alpha-beta-unsaturated dicarboxylic acids, polyhydric alcohols and natural resin acids.

4. Friction bodies, the binding agent of which comprises hardened resinous condensation products 0i! polybasic acids, natural resin acids and polyvinyl alcohol.

5. Friction bodies, the binding agent of which comprises hardened resinous condensation products of phthalic acid, glycerine and colophony.

6. Friction bodies, the binding agent of which comprises hardened resinous condensation prodnets of phthallc acid, maleic acid, colophony and glycerlne.

7. Friction bodies, the binding agent of which comprises hardened resinous condensation prod- 4 ucts of polyvinyl alcohol, maleic acid and abietic acid.

KARL WOLF. HANS BCHEUERMANN. 

